10 PRINTCHR$(147)
20 INPUT"ENTER FORMULA";F$
30 IFF$="STOP"THENSTOP
40 A=0
50 F$=F$+ " ":P$=F$:ID=9:DN=0
60 FORI=1TOLEN(P$)
65 IFMID$(P$,I,1)=" "THEN80
70 NEXT:PRINT"?INVALID FORMULA":GOTO20
80 IFI=LEN(P$)THENDN=1
90 X=I:X$=LEFT$(P$,X)
100 VA=1:V=VAL(X$)
105 IFVAL(X$)=0ANDLEFT$(X$,1)<>"0"THENVA=0
110 IFLEFT$(X$,2)="PI"THENV=3.14159265:VA=1
120 IFLEFT$(X$,1)="[255]"THENV=3.14159265:VA=1
130 IFVA=1THEN230
135 IFLEFT$(X$,1)="'"THENPRINT"ST = ";A:GOTO310
140 ID$=LEFT$(X$,1):ID=0
150 IFID$="+"THENID=1
160 IFID$="-"THENID=2
170 IFID$="*"THENID=3
180 IFID$="/"THENID=4
190 IFID$="^"THENID=5
195 IF(ID>0)AND(ID<90)ANDMID$(X$,2,1)<>" "THENPRINT"?ERROR":GOTO20
200 IFID$=" "THEN310
203 IFA=0THEN210
204 IFID$="@"THENAM=VAL(MID$(X$,2,1)):AM=-AM:GOTO207
205 IF ID$<>";"THEN210
206 AM=VAL(MID$(X$,2,1)):IFA=0THEN210
207 A=INT(A*(10^AM)+.5):A=A/(10^AM):ID=0:GOTO310
210 IFID=0THENPRINT"?BAD SYMBOL":GOTO20
220 GOTO310
230 IFID=1THENA=A+V
240 IFID=9THENA=V:ID=0:GOTO310
250 IFID=0THENPRINT"?ERROR":(null)T20
260 IFID=2THENA=A-V
270 IFID=3THENA=A*V
280 IFID=5THENA=A^V
290 IFID=4ANDV=0THENPRINT"?DIV BY ZERO":GOTO20
300 IFID=4THENA=A/V
310 IFDN=1THEN330
320 P$=RIGHT$(P$,(LEN(P$)-LEN(X$))):GOTO60
330 PRINT"RESULT = ";A:A=0:GOTO20
1000 REM NOTICE THIS PROGRAM IS STILL SUBJECT TO FLOATING POINT
1010 REM ROUND OFF ERRORS AND IS ONLY AS ACCURATE HAS BASIC PERMITS